In a manufacturing process of a semiconductor device for example, there is used a substrate cleaning apparatus for cleaning a semiconductor wafer (hereinafter, referred to as a wafer) with a cleaning solution such as a chemical solution, pure water or the like to remove contamination of particles, organic contaminants, and metal impurities adhering on the wafer. As an example of such a substrate cleaning apparatus, one that uses a two-fluid nozzle to inject a cleaning solution in a liquid drop form to the surface of a wafer is known.
Conventionally, as a two-fluid nozzle for cleaning substrates, an internal mixing type to form liquid droplets by mixing gas and liquid inside the nozzle and an external mixing type to form liquid droplets by mixing gas and liquid outside the nozzle are known (for example, refer to Patent Document 1). Also, as an example of the internal mixing type, one that allows internally-formed liquid droplets and gas to pass through a straight tube so as to accelerate the liquid droplets and inject them into the air at a sufficient speed is proposed (for example, refer to Patent Document 2).
[Patent Document 1] Japanese Patent Application Laid-open No. 2003-197597
[Patent Document 2] Patent Publication No. 3315611